Circuit breaker



Aug. 29, 1944. J. w. MAY

cmcun BREAKER Filed Dec. 26, 1941 3 Sheets-Sheet 1 INVENTOR .fohn 14/ Ma Y 4% A1'roR Y WITNESSES:

Patented Aug. 29, 1944 CIRCUIT BREAKER John W. May, Pittsburgh, Pa., aslignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa.,- a corporation of Pennsylvania Application December 26, 1941, Serial No. 424,421

24 Claims.

This invention relates to circuit breakers and more particularly to circuit breakers of the type which are tripped instantaneously in response to overload currents above a predetermined value and after a time delay on lesser overloads.

It is an object of the invention to provide a circuit breaker with an improved trip device of simple and inexpensive construction, which is op- 4 erable to trip the breaker instantaneously in response to overload currents above a predetermined value and after a time delay for persistent overloads below said predetermined value.

Another object or the invention is the provision of a circuit breaker having an improved trip device comprising an electromagnetic tripping means which is operable to trip the breaker instantaneously upon the occurrence of overloads above a. predetermined value, and a current responsive thermal trip element which is operable after a time delay in response to overloads below said predetermined value to cause the electromagnetic trip means to trip th breaker.

Another object of the invention is the provision of a circuit breaker having an improved tripping mechanism comprising an electromagnetic means energized by the current of the circuit for moving a trip member to trip the breaker, a biasing spring releasably connected to the trip member for opposing operation thereof, and a current responsive thermal element operable when heated a predetermined amount by overload current to release the trip member from the biasing spring to permit operation of the trip member by the electromagnetic means, the electromagnetic means being operable in response to overloads abov a predetermined magnitude to operate the trip member instantaneously irrespective of the opposing force of the spring.

Another object of the invention is the provision of a circuit breaker as described in the preceding paragraph, wherein the spring which opposes movement of the trip member remains connected thereto during the entire operation of the trip member by the electromagnetic means upon overloads above the predetermined magnitude.

Another object of the invention is the provision or a circuit breaker having an improved tripping mechanism including a thermally responsive trip element, the construction being such that only a very light force is required to be exerted by the thermally responsive trip element to cause a tripping operation of the breaker.

Another object of the invention is to provide a circuit 'breaker with a trip member which is biased to normal position by a spring connected thereto by a latch member which is releasable at times to disconnect the trip member from the spring, and a bimetal element operable when heated a predetermined amount in response to overload currents to unlatch the trip member from the spring.

A further object of the invention is to provide a circuit breaker with a novel trip device in which a bimetal element acts when heated a predetermined amount to disconnect a trip member from a spring biasing means which opposes tripping operation thereof, the trip member being operable on overloads above a predetermined value without disconnecting the biasing means and operable in response to overloads below said value only when disconnected from the spring biasing means.

Another object or the invention is the provision of a circuit breaker having a thermally responsive trip element and an improved means for adjusting the operating characteristic of the thermal trip element by varying the force of a, spring ensageabl with the trip element.

Another object of the invention is the provision of a circuit breaker having a current responsive bimetal trip element and improved means for adjusting the operating characteristic of the bimetal trip element and for compensating said element for changes in ambient temperature.

Another object of the invention is the provision of a circuit breaker having a current responsive bimetal trip element and an ambient temperature compensating bimetal element connected thereto by a spring means, and manually operable means for adjusting the position of the compensating bimetal element to adjust the operating characteristic of the current responsive bimetal element.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims, the invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of several embodiments thereof when read in conjunction with the accompanying drawings, in which:

Figure 1 is a vertical sectional view of a circuit breaker embodying the principles of the invention, the breaker being shown in the closed circuit position;

Fig. 2 is a fragmentary sectional view at an enlarged scale taken substantially along the line 11-11 of Fig. 1 and looking in the direction of the arrows;

Fig. 3 is an enlarged detail sectional view through the trip device taken substantially on line III-1II of Fig. 2 and showing the position of the parts when the trip member is operated by the electromagnet after release from the spring means by the bimetal element:

Fig. 4 is a sectional view similar to Fig. 3 show ing the position of the parts when the trip memher is operated by the electromagnet without having been released from the spring means;

Fig. 5 illustrates a modification of the invention and represents a sectional view taken on line V-V of Fig- 6;

Fig. 6 is a plan view of the modified trip device shown in Fig. 5;

Fig. 7 is a detail sectional view taken substantially on line VII-VII of Fig. 5 and showing the latch for connecting and disconnecting the trip lever from its biasing means; and

Fig. 8 is a fragmentary detail view showing the method of adjustably securing the scale plate to the trip device.

Referring to Figure 1 of the drawings, the multipole circuit breaker mechanism is mounted on a base ll of insulating material and a casing l3 may be provided to enclose the mechanism. The mechanism is supported on a frame structure I8 comprising a pair of substantially parallel side walls I! (only one being shown) connected adjacent the base H by a cross member IO, secured to the center portion of the base II by means of bolts 2i and 23. The bolt 23 extends through the cross member is and serves to rigidly secure a. connector 21 of conducting material to the cross member. The sides l1 are also joined by a cross member 25 at their outer ends to form a rigid framework for supporting the breaker mechanism.

A contact arm for the center pole of the breaker is provided with a pair of spaced arms 3| pivotally mounted on a pivot comprising a shaft 29 extending through an opening in the connector 21 and mounted in openings in the sides of the frame It. The arms 3| are disposed one on each side of the connector 21 and are pivoted on the ends of the shaft 28 which project beyond the sides of the connector and into openings in the sides of the frame ii.

The contact arm 30 pivotally carries a main contact member 41 pivotally mounted on a pivot 49 supported in projections 5| (only one being shown) of the contact arm 3.. A contact 33 secured to the contact-member 41 cooperates with a stationary contact 39 mounted on a conductor 4! secured to the base II by bolts 43. The conductor 4| is bent at right angles and extends through an openingdn the base II to form a terminal connector 45.

An arcing contact member I! is pivoted on a pivot pin 51 supported in projections u of the contact arm 30. The contact member has secured thereto an arcing contact shoe II which cooperates with a stationary arcing contact 31 secured to an arcing horn 30, the arcing horn being secured to the conductor ll by means of screws 38.

A spring 53 compressed between a spring seat on the contact member 41 and a spring seat on the contact arm 33 provides contact pressure for the contacts 33-". Similarly a spring 33, surrounding a rod ii pivotally connected to the arcing contact member 55, and compressed between a washer on the rod and a spring seat on the contact arm 33 provides contact pressure for the arcing contacts 35-31. The rod ll extends through and is slidable in an opening in the upper end of the contact arm 33.

The circuit breaker is of the multipole type, each pole thereof being provided with a contact arm 30 (only one being shown). The contact arms for the outer poles are not provided with arms 3| but are securely clamped on a tie bar II which is clamped to the contact arm 30 of the center pole by a clamp 13 and bolt H, the poles being insulated from each other by a sheath of insulating material 0! between the tie bar 31 and the contact arms 3|. All of the contact arms of the breaker, therefore, operate as a unit to simultaneously operate the contacts for all of the poles of the breaker. The stationary main and arcing contacts and the movable main and arcing contacts of the two outer poles are of the same construction as the contact means of the center pole shown and described.

When the contact arm 30 is rotated in a clockwise direction (Fig. 1) to open the contacts, as will be described later, the springs 53 and 03 rock the contact members 41 and 55, respectively, counterclockwise about their pivot pins. This movement of each contact member 41 is limited by a projection 13 thereon striking the body of the contact arm 30. The counterclockwise movement of each contact member 55 is limited by a nut 15 on the end of the rod 6| striking the contact arm 30. The adjustment of the nut 15 on the rod II is such that the main contacts 3333 open shortly before the arcing contacts 35-31 open.

The arc, resulting from the rupture of the circuit, is dissipated by an arc extinguisher 16 of which three are provided, one for each pole of the breaker. Each of the arc extinguishers comprises, generally, a stack of slotted plates disposed adjacent the path of travel of the arcing contact 35. These plates cause the arc to be drawn in a direction towards the ends of the slots which results in breaking up the are into a number of small arcs and causes said arcs to be quickly cooled and extinguished.

The electrical circuits for the several poles of the breaker are substantially the same, each circuit extending from the terminal 45 through the contact member H, the stationary main contact 38, the movable main contact 33, the contact member 41, a flexible shunt conductor 13 connecting the contact member 61 to the connector 21, a terminal 12 secured to the connector 21 by bolts H, a conductor ll having its one end secured to the terminal 12 and its other end secured to a conductor 8|. The conductor II is bent at substantially right angles and projects through an opening in the base II where it forms a terminal 33 which, together with the terminal 45, serves to connect the breaker in an electrical circuit.

The circuit for the arcing contacts extends from the conductor 4| through the contacts 31 and 35, the arcing contact member ll, a flexible shunt conductor 11 to the main contact member 31 and thence over the circuit previously described to the terminal 33.

The contact arm 30 is biased in a clockwise direction toward open position by a pair of springs ll having one end connected to the contact arm 30 near its free end, and the other end hooked to a fixed pivot pin 31 supported in the frame It. Under normal circuit conditions, the contact arm 30 is releasably restrained in closed circuit position (Fig. 1). by means of a' linkage and toggle arrangement forming the operating mechanism described as follows: v

A lever 39 comprising a pair of parallel levers joined by an integral cross member H1 is pivotally mounted on a fixed pivot 9I supported in the frame I5. The lever 99 is connected to the arms 3| of the contact arm 30 by means of a main operating toggle comprising toggle links 93 and 95. The toggle link 95 comprises a pair of links (only one being shown) joined by a cross member H and is connected to the-arms 3I by a pivot pin 99. The toggle links 93 and 95 are pivotally connected by a knee pivot pin 91 and the link 93 is pivotally connected to the lever 99 by a pin IOI. A link I03 connects the free end of the lever 99 to one end of a lever I05 pivoted on the fixed pivot 91. The other arm of the lever I05 is pivotally connected to one end of a toggle link I01 which has its opposite end pivotally connected to a toggle link I09 by a knee pin III, the toggle link I09 being pivoted on a fixed pivot II3 supported in the frame I5. The

toggle link I01 comprises a pair of links Joined by a yoke II9 having a bent out portion I2I, the purpose of which is to cooperate with manually operable means to trip the breaker as will be later described. The toggle link I09 comprises a pair of links joined at their ends adjacent the pivot II3 by a yoke I23 having formed portions I25 and I21 thereon.

The linkage just described serves to releasably hold the contact arm and consequently the contacts in closed position. When the contact arm 30 is in the closed contact position, the main operating toggle 93-95 is overcenter above a line through the centers of the pins 99 and IN, and the toggle comprising the link 93 and the lever 89 is overcenter above a line through the center of the knee pin 91 and the fixed pivot 9I. The overcenter movement of the toggles 93-95 and 93-99 is limited by a projection I20 on the link 93 striking the cross member II5 joining the links 95. In this position, the lever 99 is biased in a clockwise direction by the springs 95 but is prevented from rotation by the tripping toggle I01-I09 being biased overcenter to the left of a line through the fixed pivot H3 and the point of connection of the toggle link I01 and the lever I05 by a spring I23, tensioned between the yoke H9 and the fixed pivot H3. The overcenter position of the toggle I01-I09 is adjustably limited by the formed portion I25 of the yoke I23 striking an adjusting screw I29 in the cross member 25 of the frame I5.

It can be seen that the force exerted by the springs 95 on the contact arm 30 is transmitted through the linkage just described and applied to the tripping toggle I01-I09 which, in its overcenter position (Fig. l), is effective to hold the contacts in closed.position. The tripping toggle I01-I09 is adapted to be moved overcenter in an outward direction to collapsed position to cause opening of the contacts, by a trip device indicated generally at I33 (Figs. 1, 2, 3 and 4) which acts through a trip rod I35.

The trip rod I35 is slidably supported in a shunt trip electromagnet coil enclosed in a casing I38 secured to the frame I5. The coil is adapted to be energized by a shunt circuit (not shown) or by a manually controlled switch to operate the trip rod I35 from a distance in a manner well known in the art.

The trip device I33, when operated in response to overload current, is adapted tothrust the rod I35 upwardly, in a manner to be described later. When the trip rod I35 is thrust upwardly, the upper end thereof strikes the formed portion I21 on the yoke I23 and rocks the tripping toggle link I09 clockwise (Fig. 1) about its pivot II3 moving the tripping toggle I01-I99 overcenter in a direction to cause its collapse. i

When the tripping toggle I01-I09 moves overcenter, it permits the springs 05, acting through the contact arm 30 and the main operating toggle 93-95 to rock the lever 99 clockwise about its pivot, which movement is transmitted through the agency of the link I03 to rock the lever I05 clockwise and complete the collapse of the tripping toggle I01-I09. The main operating toggle 93-95 does not immediately break overcenter but travels as a unitary linkage with the contact arm 30 and the lever 99 until the movement of the contact arm 30 is arrested by the arm striking a stop portion I31 of the frame structure I5. When this occurs the inertia of the toggle link 95, including the comparatively heavy cross member H5, is such that the toggle 93-95 is forced overcenter in a direction to cause its collapse. By the time the knee pin 91 of the main toggle has passed below the center line 99-IOI, the weight of the linkage and parts causes the main toggle to collapse and causes the lever 39, the link I03, lever I05 and the tripping toggle I01-I09 to be automatically reset to their normal positions as shown in Fig. 1.

When the main toggle 93-95 has collapsed, the force of the springs 95 is no longer applied to the tripping toggle I01-I09 and the spring I29 assists the weight of the parts in immediately restoring the latter toggle to its overcenter position and in restoring th lever I05, link I03 and lever 09 to their normal positions. The main toggle 93-95 remains in collapsed condition until the contacts are reclosed which may be effected either automatically or manually.

In order to close the contacts manually, an operating handle I4I is provided. This handle is rotatably mounted in a frame I43 of insulating material secured to the main frame structure II. A link l5l, adapted to be thrust downwardly (Fig. 1) by a crank arm (not shown) on the handle shaft upon clockwise or closing movement of the handle I, is notched at its lower end and engages an hour glass-shaped roller I53 mounted for rotation on a cross member I41 forming the outer end of a contact closing lever I45. The lever I45 comprises a pair of substantially parallel spaced levers I45 pivotally mounted on the fixed pivot 9I and rigidly joined at their outer ends by the cross member I41 which carries the roller I53. The other ends of the levers I45 are rigidly connected by a cross bar I49. Projections I52 on the cross bar I49 support a pivot I51 upon which is rotatably mounted a roller I55. The levers I45 straddle the frame I0.

Downward movement of the link I5I' rocks the contact closing lever I45 clockwise about its pivot 9| during which movement the roller I55 engages the collapsed main toggle 93-95 and moves this toggle to its overcenter position. Straightening the toggle 93-95 rotates the contact arm 30 counterclockwise to close the contacts and tension the springs 95, since the pivot IOI of the operating toggle is'held in fixed position by the linkage I03, I05, I01 and I09.

After the contacts are closed the handle III is released whereupon a spring I33, tensione'd between the frame I3 and the contact closing lever I33 rocks the lever counterclockwise to its normal position. This movement thrusts the link "I upwardly and returnsthe operating handle I" to its neutral position.

The contacts may be closed electrically by means of a motor I33 mounted on a support frame I33 secured to the main frame I3 by an insulating plate I32. The motor may be energized from any suitable source and in a manner well known in the art. When energized, the motor is adapted, through a suitable reduction. gearing, to retate a crank disc I30 which carries an anti-friction roller I3I. The roller strikes a curved face I32 on an arm I33 secured to the side of the contact closing lever I33 and rocks the lever clockwise to close the contacts in the previously described manner. As soon as the roller I3I passes out of engagement with the arm I33, the spring I33 acts to restore the contact closing lever I33 to its normal position (Fig. 1). The motor I33 is deenergized by a suitable limit switch (not shown).

The breaker may also be tripped open manually by proper manipulation of the handle I3 I. When the handle is rotated in a counterclockwise or tripping direction, a projection (not shown) on the thrust link I5I engages the previously described projection I2I on the yoke II! of the tripping toggle link I01 and moves the tripping toggle III1I33 overcenter in a direction to cause its collapse. This causes opening of the contacts in the manner previously set forth.

As was stated previously, the trip rod I33 is thrust upwardly to trip the breaker by operation of the trip device I33 in response to overload conditions in the circuit controlled by the breaker. A plurality of trip devices I33 is provided one for each pole of the breaker. It is to be understood, however, that a trip device may be provided for at least two of the poles of the breaker and will function in the same manner to trip the breaker. Since the trip devices are alike, only one will be described.

Each of the trip devices I33 (Figs. 1, 2, 3 and 4) includes a laminated U-shaped magnet core HI and a frame comprising spaced parallel members I33 joined by a cross member I33. The ends of the frame member I63 adjacent the magnet core I6I are bent at right angles to form mounting feet I31 abutting against the core I3I, and bolts I39 pass through openings in the feet I31, the core I3 I and the base II to rigidly secure the frame I33 and the core I3I to the base. A spacer ill of insulating material is provided between the magnet core I3I and the base I I.

A trip lever comprising a pair of spaced parallel levers I13 is pivotally supported on a pivot pin I13 mounted in the frame members I33. The levers I13 are rigidly connected at their outer ends by a cross member I11, and a laminated armature I19 is secured to the oposite ends of the levers so as to cooperate with the magnet core I3I The magnetic air gap is adiustably determined by a screw I38 in the cross member I33 of the frame I33, the screw serving to limit the clockwise movemerit of the trip lever I13.

Each of the cross members I11 has an adjusting screw I3I mounted thereon and a lock nut I33 is provided to lock the screw in its adjusted position.

Upon operation of the trip lever I13 in response to an overload current in the circuit of its correspending pole, the screw I3I ing arm I33 fixed on a trip mounted in a bracket I33 secured I33,androckssaidtripbarin aclockwisedireetion. The trip bar I31 extends across all of the polesofthebreakerandanarm illispro'vided for each pole. One of the arms I33 is in alignment with the trip rod I33and. upon clockwise movement of the trip bar I31, the rod I33 is thrust upwardly to trip the breaker in the manner previously described.

The trip lever I13 is biased against operation by the magnet core by a pring Ill tensioned between the cross member I11 and a spring anchor I33 in a formed projection I33 of the cross member I33 of the frame I33.

A lever comprising a pair of spaced arms I31 (Figs. 2, 3 and 4) is pivotally mounted on the pivot pin I13. These arms I31 are rigidly connected by pivot pins 233 and 231. A latch 233 pivotally supported on the pin 233 is provided with a shoulder III and is biased by a spring 2I3 into engagement with a latch member 2I3 secured to the cross member I11 of the trip lever.

A link comprising a pair of spaced arms 2" disposed one on each side of the latch 233. is pivoted on the pin 231. The arms 2I1 are rigidly connected by a yoke 2" which is provided with an extension 22I. A pin 223 fixed in the latch 233 projects through elongated slots 223 (Figs. 3 and 4) in the arms 2I1 to operatively connect the link to the latch 233.

A bimetal element 221 is disposed along the upper side of the heater portion of the conductor 13 and both the bimetal element and the heater portion of the conductor 13 are securely fastened to a bracket 223 by rivets 23I (Fig. 3). The bracket 22! extends between the side members of the frame I33 and is suitably secured thereto.

An adjusting bimetal element 233 is provided with ears 233 which are pivotally supported on a pin 231 mounted in the depending ends of a bracket 233 secured to the under side of the cross member I33 01' the frame I33. A spring I has one of its ends hooked in a spring anchor 233 of insulating material secured to the current responsive bimetal 221 at a point near its free end. The other end of the spring 2 is connected to a spring anchor 233 of insulating material secured to the left hand end (Figs. 3 and 4) of the bimetal 233. The spring 2 passes through an opening in the cross member I33 of the frame I33. The tension of the spring 23I holds the right hand end (Fig. 3) of the pivoted bimetal element 233 in contact with the tip of an adjusting screw 231 mounted in the formed portion I33 of the cross member I33.

One of the arms of the lever I31 is provided with an extension 23I to the end of which is attached one end of a biasing spring 233 having its other end attached to a movable plate 233. An adjusting screw 231 (see Fig. 8) which passes through an opening in the formed portion I33 of the cross member I33, cooperates with the plate 233 and serves to move the plate up and down, depending on the direction of rotation of the screw. for the purpose of adjusting the tension of the spring 233.

When the shoulder 2 of the latch 233 \Figs. 1 and 4) is in engagement with the latch member 2i 3, the spring 233 is effective to bias the trip lever I13 against tripping movement.

The movable parts of the trip device are shown in Fig. l in the positions the assume under normal circuit conditions. Current oi rated value flowing through the circuit of any pole oi the breaker and, therefore, through the heater portion or the conductor 13 and through the conductor II which passes between the legs 01 the magnet core I3I, causes but slight energization of the magnet. The pull of the magnet under normal conditions is not suiiicient to overcome the combined force of the two springs "I and 253. Also normal current flow through the heater element 13 does not heat the bimetal element 221 sumciently to cause it to flex from its normal shape.

Upon the occurrence of a continuous overload below a predetermined value, for instance, below approximately .1000 percent of normal, the bimetal element 221 is heated by the overload current and when heated a predetermined amount it flexes in an upward direction. When the bimetal flexes in response to an overload current, an adjusting screw 243, secured by a lock nut at a point near the free end oi the bimetal 221, engages the extension 22I oi the trip member 2| 1 and rocks the link clockwise about its pivot 201. This movement of the trip member, due to the pin and slot connection 223-225 rocks the latch 203 counterclockwise and unlatches the trip lever I13 from the spring biased lever I31. Since the biasing efl'ect of the spring 253 is no longer applied to the trip lever I13, the electromagnet I3I now overcomes the tension 01' the light spring HI and operates the trip lever I13 to trip the breaker in the previously described manner. The force exerted by the electromagnet at or slightly below normal rated current is sufficient to move the trip lever I13 to tripping position against the tension of the spring Hi to trip the breaker when the latch 233 is released. a

As soon as the flow of current is interrupted by opening of the contacts and the electromagnet is deenergized, the spring I3I acts to restore the trip lever I13 to its normal position (Fig. 1), and, as the bimetal element cools and resume its normal shape, the spring 2 I5 rocks the latch 203 clockwise to reengage the shoulder 2 with the latch 2I3 of the trip lever I13. I

The bimetal element due to the time it takes to be heated a suillcient amount to flex, thereby provides a desirable time delay during which the abnormal current may return to normal without causing circuit interruption.

The trip'device is constructed to instantaneously trip the circuit breaker upon the occurrence of an overload above the predetermined value, that is, 1000 percent or more of normal current, or a short circuit. This value is, oi course, variable by the adjusting screw 251. In this event the breaker s tripped and the current ruptured before the bimetal element is heated an appreciable amount and, therefore, the latch 203 is not operated to disconnect the spring 253 from the trip lever I 13. The magnetic energy on such overloads is sufllcient to overcome the combined force of both the springs I3I and 253 and trip the breaker. Since the latch 203 remains latched to the trip lever I13, the counterclockwise or tripping movement of the lever I13 rocks the spring biased lever I31 about the pivot I15, the spring 2I5 acting to maintain the latch 209 in engagement with the latch member 2I3 on the lever I13. During this action, the pin and slot connection 223-225 permits relative movement of the link 2" and -thespring 2.

the latch 233. The parts are shown in th instantaneously tripped position in Fig. 4. The springs III and 253 restore the parts to normal unstripped positions when the circuit is interrupted.

The movable plate 255 (Figs. 3, 4 and 8), to which the spring 233 is attached. is provided with a pointer 253 which projects through a guide slot 2" in a scale plate 233. This scale plate is adjustably mounted on spaced extensions 235 integral with the formed projection I35 01' the cross member I35, by means 0! screws 231 (Fig. 8) in the extensions andslots 233 in the sides oi the scale plate. The scale plate 233 bears a scale (not shown) which indicates the instantaneous tripping point of the breaker. Obviously rotating the screw 231 will move the plate 255 up or down and vary the tension of the spring 253 according to the direction the screw is turned. Varying the tension of the spring 253 varies the instantaneous tripping point of the breaker, and the pointer 253 which moves with the plate 255 indicates the percentage of overload current at which the breaker will trip.

The pivoted bimetal element 233 (Igs. 1, 3 and 4) serves to manually adjust the tension oi Turning the screw 231 causes the bimetal 233 to rotate either clockwise to decrease the tension 01' the spring or counterclockwise to increase the tension according to the direction the screw is turned. Varying the tension of the spring 2 varies the minimum overload tripping current at which the bimetal element will flex when heated to release the latch and cause trippins of the breaker.

The bimetal element 233 serves the additional purpose of automatically varying the tension 01' the spring 2 according to variation in air temperature. The bimetal 233 is disposed to flex downwardly in response to an increasing ambient temperature thus varying the tension of the spring 2 and counteracting the eil'ect oi the ambient temperature on the bimetal element 221.

Figs. 5, 6 and 7 illustrate a modified embodiment oi the invention in which the bimetal element acts directly on the latch to disconnect the trip lever from its biasing spring. Certain of the parts in the illustrative embodiment of the modification are the same as corresponding parts in the previously described embodiment and have been given the same reference characters.

Referring to Fig. 5, a U-shaped 'bimetal element 2" is rigidly and electrically secured to a shunt conductor 213 which is secured to the end of terminal conductor 33. Adjacent the upper leg 0! the bimetal 2", the shunt conductor 213 is electrically secured to a conductor 215 which extends upwardly and may be secured to the connector 21 (Fig. l) in a suitable manner. Pivotally mounted on the pivot pin I15 is a lever 213 comprising a pair of parallel arms 211 and 213 rigidly connected near the pivot I15 by a yoke Ill. The arms 211 and 213 extend downwardly and are bent towards each other (see Fig. 6), the am 211 extending toward the right (Fig. 5) a greater distance than the arm 213. The arm 213 is bent at right angles toward the am 211 as at 233 (Fig. 6) and is then bent back parallel to and adjacent to the arm 211 at 235, the portion 235 being secured to the arm 211. A spring 231 has its upper end connected to a spring anchor 233 on the free end of the arm 211 and its lower end connected to an anchor 23i secured to a movable plate 233. An adjusting screw 235 supported in the extension I33 of the frame I33 is rotatably connected to the plate ill in such a manner that rotation oi the screw ill shiits the plate "I up or down, depending on the direction the screw 2" is rotated, to vary the tension oi the spring I" and consequently the instantaneous tripping characteristic. The spring 281 biases the'lever I'll in a clockwise direction against the cross member ill oi the irame i. Reierring to Fig. 'l, a latch 2" pivoted on a pivot pin 2" supported on the bent portion 288 of the arm I", is biased by a leaf spring Ill into latching engagement with a latch member "I secured to the under iace oi the cross member I" oi the trip lever I13. It can thus be seen that the spring biased lever I'll is'operatively connected to the trip lever I'll and that thereiore, the spring ll! is normally eiiective to bias the trip lever I'll against the attraction oi the electromagnet ill.

The iree end of the bimetal element I'll carries an adjusting screw 3", the end which projects inwardly and is adapted, when the bimetal element is heated a predetermined amount in response to an overload, to engage the latch 2" and rock the latch clockwise (Fig. '7) to disconnect the trip lever l'll' irom the influence of the spring I". When the lever ill is ireed from the tension oi the spring 2", the pull oi the electromagnet iii is suiilcient to overcome the tension oi a light spring 801, tensioned between a projection on the armature I'll and a projection I" on the base II, and to operatethe trip lever I'll to trip the breaker.

As in the orignial embodiment the force exerted by the electromagnet at or slightly below normal rated current is suiilcient to move the trip lever I'll to tripp position against the tension of the spring 3" to trip the breaker ii the latch I" isreleased.

The spring 301 rocks the trip lever Ill clockwise to normal position when the breaker opens and the electromasnet III is deenergized. The spring Ill reengages the latch Ill with the latch member I" when the bimetal has cooled and resumed its normal position.

Upon the occurrence of an overload above the predetermined value or a short circuit, the bimetal I'll does not have tim to become heated a suilicient amount to cause unlatching oi the trip lever I'll irom the spring-biased lever 216. The pull of the electromagnet is great enough however to overcome the combined iorce oi the springs Ill and 301 and cause instantaneous tripping oi the breaker. Since the latch 29'! remains eiiective the lever I'll is rocked counterclockwise against the tension oi the spring 281. Upon deenergization oi the electromagnet the spring 281 rocks the lever 2'" clockwise and, due to the latch connection 291-403, rocks the trip lever I'll clockwise to normal position aided by the spring 301.

The minimum tripping point of breaker under the control of the bimetal 2' may be varied by adjustment oi the screw "5, and the instantaneous tripping point or the modified trip device may be varied by adjustment of the screw 29!. A pointer Ill (Fig. 5) is provided on the movable plate 293 which pointer cooperates with the scale plate 2" to indicate the percentage oi overload current at which the breaker will be tripped instantaneously.

The breaker is trip free under all conditions, that is the contacts will be automatically opened ii the handle ill is held in the closed position against an overload current or ii an at empt should be made to close the contacts against an overload.

It can be readily seen that the toggle and linkage structure oi the operating mechanism acts to reduce the tripping load to a minimum. the load on the tripping toggle Ill-ill being such that a very small iorce is required to trip the breaker. This is made possible by omitting latch mocha nlsm from the operating mechanism. I

The parts oi the trip device are constructed to cooperate with the operating mechanism to imther reduce the tripping eiiort required oi the bimetal element. It will be noted that the bimetal does not directly trip the breaker but serves, when heated a predetermined amount to disconnect at least a part oi the biasing means iron the trip member so that the latter may operate to more quickly trip the breaker. The operating characteristic oi. the bimetal element is varied to compensate ior ambient temperature by the use oi a thermal element resiliently connected to the bimetal element and the thermal element is provided with a manual adjustment. The trip device iorms a unitary structure which may be easily removed irom the breaker so that another trip device may be substituted.

Having described several embodiments oi the invention in accordance with the patent statutes, it is to be understood that various changes and modifications may be made in the structural details disclosed without departing irom some oi the essential ieatures oi the invention. It is, thereiore, desired that the appended claims be given as reasonably broad interpretation as the prior art permits.

I claim as my invention:

1. In a circuit breaker, a switch member biased to open position, operating mechanism ior said switch member comprising an operating toggle connected to the switch member, a linkage connected to the toggle for holding one end oi the toggle in operative position, said linkage constituting the sole means ior holding said end oi the toggle in operative position, and a trip device comprising a member operable to move the linkage to eiiect an opening operation oi the switch member, a plurality oi biasing means opposing operation of said member, and a bimetal element iixedly secured at one portion thereof to a iixed supp rt and operable in response to overload currents to disconnect one of said biasing means from the trip member.

2. In a circuit breaker, a switch member biased to open position, operating mechanism ior said switch member comprising an operating toggle connected to the switch member, a load reducing linkage connected to one end oi the toggle said linkage comprising the sole means ior holding said one end of said toggle in operative position. and a trip device operable to move the linkage to cause opening operation of the switch member, said trip device comprising a trip lever, biasing means opposing operation oisaid trip lever, a pivoted connection ior releasably connecting a part of said biasing means to said trip lever, electromagnetic means responsive to overloads ior operating the trip lever, and thermally responsive means operable when heated a predetermined amount ior operating said connection to disconnect at least a part of the biasing means irom the trip lever.

3. In a circuit breaker having a switch member biased to open circuit position, operating mechanism therefor comprising an operating oggle connected to said switch member, a linkage for holding one end of the toggle in operative position, and a trip device operable to move said linkage to cause an opening operation of the switch member, said trip device comprising a trip lever operable to move said linkage, means biasing said trip member against operation at least a part of said biasing means being releasably connected to said trip member, and a bimetal element fixedly secured at one portion to a fixed support and operable when heated a predetermined amount in response to overload currents to disconnect the releasable part of the biasing means from the trip member.

4, In a circuit breaker, a. switch member biased to open position, operating mechanism for said switch member including anoperat'ng toggle connected to the switch member, a linkage connected to on end of said toggle for holding said toggle in operative position, and a :trip device operable to move said linkage to eilect an opening operation of the switch member, sa d trip device comprising a trip lever, an electromagnet operable in response to overload currents above a predetermined value to operate the trip lever, means biasing said trip lever against operation, a pivoted latch for releasably connecting a part of said biasing means is said lever, and a bimetal element operable when heated a predetermined amount to operate said latch and disconnect the releasable portion of the biasing means from the trip lever to permit said electro-magnet to operate the trip lever to trip the breaker in response to overloads below said predetermined value.

5. In a circuit breaker, a switch member biased to open position, operating mechanism for said switch member including an operating toggle connected to the switch member, a linkage connected to the toggle for holding one end of said toggle in operative position, and a trip device comprising a trip lever operable to move said linkage to caus opening operation of said switch member, electro-responsive means for operating the trip lever, a plurality of springs biasing said trip lever against operation, a latch for releasably connecting at least one of said springs to said trip lever, and a bimetal element operable when heated a predeterm ned amount for operating the latch, said latch being mounted for movement independently of said bimetal element.

6. In a circuit breaker, a switch member biased to open position, operating mechanism for said switch member, and a trip device comprising a lever operable to cause an opening operation of the switch member, means biasing said lever against operation, electro-magnetic means responsive to overload currents to operate said lever, a bimetal element responsive when heated a predetermined amount to render a part of the biasing means ineil'ective, and a member thermally responsive to ambient temperatures resiliently connected to said bimetal element.

"1. In a circuit breaker, a switch member biased to open position, operating mechanism for said ,switch member, a trip device comprising a trip member operable to cause an opening operation of the switch member, means biasing said trip member against operation, electromagnetic means operable in response to overload currents to operate the trip member, a bimetal element responsive when heated a predetermined amount to render at least a part of the biasing means inefiective, a thermal member, and a spring connectins said thermal member to said bimetal element,

said thermal member being responsive to ambient changes in temperature to vary the tension of the spring and compensate for the effect of ambient temperature on the bimetal element.

8. In a circuit breaker, a switch member biased to open position, operating mechanism for said switch member, a trip. device comprising a tri member operable to cause an opening operation or the switch member, means biasing said trip memberagainst operation, an electro-magnet for operating the trip member in response to overload currents, a bimetal element operable when heated a predetermined amount to render at least-a part of the biasing means ineffective to oppose operation of the trip member, a thermal member, a spring connecting said thermal member to the bimetal element, said thermal member being responsive to ambient temperatures to vary the tension of said spring, and means to manually adiust the thermal member to vary the tension 01' the spring.

9. In a circuit breaker, a switch member biased to open position, operating mechanism for said switch member comprising an operating to le connected to said switch member, a linkage connected to the toggle for holding one end of said toggle in operative position, and a trip device comprising a lever operable to move said linkage to eflect an opening movement of the switch member, a plurality of means biasing said lever against operation, one of said biasing means being adjustable to vary the tripping characteristic of the breaker, electromagnetic means responsive to overloads for operating the lever, and a thermally responsive element operable in response to overload currents below a predetermined value to disconnect the adjustable biasing means from the lever.

10. In a circuit breaker, a switch member biased to open position, operating mechanism for the switch member, a trip device comprising a trip member operable to cause an opening operation of the switch member, an electro-magnet for operating said trip member upon the occurrence of an overload above a predetermined value, means biasing the trip member against operation, a latch member connecting the biasing means to said trip member, a current responsive bimetal element responsive when heated a predetermined amount to disconnect the trip member from the biasing means, a pivoted thermal member, a spring tensioned between the thermal member and the bimetal element, said thermal member being responsive to ambient temperatures to vary the tension of said spring, and manually operable means to rotatably adjust said thermal member.

11. In a circuit breaker, relatively movable contacts, a switch member for opening and closing said contacts, said switch member being biased to open position, operating mechanism for said switch member, a trip device comprising an electromagnet, a member operable by said electro-magnet for causing an opening operation of the switch member, means for biasing said member against operation, a pivoted latch member for at times disconnecting the member from said biasing means, and a bimetal element mounted on a fixed support and operable in response to overload currents to move the latch to disconnect themember from the biasing means, said bimetal element constituting the sole means for operating said latch.

12. In a circuit breaker, a switch member biased to open position, operating mechanism for said switch member including a linkage operable to cause opening of the circuit, a trip device comprising a trip member, an electro-magnet tor-op. erating saidtrip member in response to overload currents, means for biasing said trip member against operation, pivoted means operable at times to disconnect the trip member from the biasing means, and a bimetal element operable when heated a predetermined amount in response to overload currents below a predetermined value to operate said pivoted disconnecting means, said bimetal element constituting the sole means for operating the disconnecting means.

13. In a circuit breaker, a switch arm biased to open position, operating mechanism for said switch member including an operating toggle connected to said switch member, a load reducing linkage connected to said toggle for holding one end of said toggle in operative position, a trip device comprising a trip member operable to move the linkage to eiiect opening of the circuit, means biasing said trip member against operation, electro -magnetic means operable in response to overload currents to actuate the trip member, and a bimetal element mounted on a fixed support and operable in response to overloads below a predetermined value to disconnect the trip member from the biasing means, said electro-magnet being operable in response to overloads above said predetermined value to actuate the trip member without disconnecting trip member from the biasing means.

14. In a circuit breaker, a switch arm biased to open position, operating mechanism for said switch arm including a linkage movable to cause opening of the circuit, a trip device comprising a trip member operable to move said linkage, an electro-magnet for actuating the trip member in response to overload currents, an arm biased against operation, a latch pivotally supported on said arm and normally latching said arm to the trip member, a lever pivotally supported on said arm, said lever being operable to unlatch the trip member, and a bimetal element operable when heated a predetermined amount in response to overload currents for actuating said lever.

15. In a circuit breaker, relatively movable contacts,-operating mechanism including a linkage operable to cause opening of the contacts, a trip device operable in response to overload currents to actuate the linkage, said trip device comprising a trip member, an arm biased by a spring against operation, a latch plvotally supported on said arm operatively connecting said arm and the trip member, a lever pivotally supported on the arm and operatively connected to said latch, a bimetal element operable when heated a predetermined amount in response to overload currents to actuate said lever and unlatch the spring biased arm from the trip member.

16. In a circuit breaker, a switch member operable to open and close the circuit, operating mechanism therefor, a trip device comprising a trip member operable to cause an opening operation of the switch member, a bimetal element ass-1,217

pensate for the eflect oi ambient temperatures on the bimetal element, and means cooperating with said thermal element at a point spaced from the point of attachment of said resilient means to manually vary the tension of the resilient means.

17. In a circuit breaker, a switch'member openable to open and close the circuit, operating mechanism (or said switch member, a trip device including a trip member operable to cause an opening operation oi the switch member, abimetal element operable in response to overload currents to eflect operation of the trip member, a spring connected to said bimetal element, and manual means separate from said bimetal element and operable to vary the tension oi said spring to thereby vary the operating characteristic of said bimetal element. r

18. In a circuit breaker, a switch member biased to open position, operating mechanism for said switch member, a trip device including a trip member operable to cause an opening operation or the switch member, biasing means opposing operation of the trip member, a bimetal element operable in response to overload currents to disconnect said biasing means from the trip member, and resilient means connected to the bimetal and adjustable to vary the operating characteroperable when heated a predetermined amount vary the tension of the resilient means to comis istic of the bimetal.

19. In a circuit breaker, a switch member biased to open position, operating mechanism therefor including an operating toggle connected to the switch member, said operating mechanism including means for moving the switch member to closed position, a linkage for holding one end of the operating toggle in operative position, said linkage including a tripping toggle and constituting the sole means for holding the operating toggle in operative position, a trip device including a trip member operable to move said tripping toggle to eil'ect an opening operation of g the switch member irrespective of the position of the closing means, a plurality oi biasing means opposing operation or the trip member, at least one of the biasing means being releasably connected to said trip member, means for adjusting the releasable biasing means to vary the tripping characteristic of the device and a bimetal element operable when heated a predetermined amount in response to overload currents to disconnect the releasable biasing means from the trip member.

20. In a circuit breaker, a witch member biased to open circuit position, operating mechanism therefor including a toggle connected to said switch member, a linkage including tripping toggle, said toggle comprising the sole means for holding the operating toggle in operative position, a trip device operable to move said linkage to cause an opening operation oi the switch memher, said trip device comprising a trip member operable to actuate the tripping toggle, biasing means opp ing operation of said trip member, at least a part oi said biasing means being releasably connected to said trip member, manual means for adjusting the releasable biasing means to vary the tripping characteristic of the device and a bimetal element operable when heated a predetermined amount in response to overload currents to disconnect the releasable biasing means from the trip member.

21. In a circuit breaker, a switch member, operating mechanism for said switch member, a trip device comprising a trip member operable to cause an opening operation of the switch member, biasing means opposing operation of the trip member, a bimetai element operable in response to overload current below a predetermined value for disconnecting the trip member from the biasing means, an armature on the trip member, an electro-magnet core responsive to overload currents for attracting the armature to operate the trip member, and a rigidly mounted energizing conductor for the electro-magnet, said bimetal element being secured to said conductor and at least a portion oi. said bimetal ele' ment being disposed in intimate contact with the energizing conductor, said electromagnet being operable at times to operate the trip member without said biasing means being disconnected from said trip member.

22. In a circuit breaker. a switch member biased to open position, operating mechanism for said switch member, a trip device including a trip member, biasing means opposing operation of the trip member, an armature on said trip member, an electro-magnetic core for operating the armature to cause an opening operation of the switch member, a fixedly mounted energizing conductor for said magnet core, a non-current carrying bimetal element secured to said conductor and having at least a portion disposed in intimate contact with said conductor and operable when heated a predetermined amount in response to overload currents to disconnect the trip member from the biasing means, said electromagnet at times operatins said trip member irrespective of the connected condition of said biasing means said trip device comprising a unitary structure removably mounted on the circuit breaker.

23. A trip device for a circuit breaker comprising a trip member operable to cause opening of said breaker, means biasing said trip member against operation, current responsive means operable when heated a predetermined amount in response to overload currents to disconnect said trip member from the biasing means, a thermal element,resilient means connecting said current responsive means to said thermal element, said thermal element being operable in response to changes in ambient temperature to vary the tension of said resilient means t0 c0mpensate the current responsive means for the influence of ambient temperatures, and means to manually vary the tension of said resilient means.

24. A trip device for a circuit breaker comprising a trip member operable to eflect opening of said breaker, biasing means opp in operation oi the trip member, an electro-responsive element operable in response to overload currents to disconnect said biasing means from the trip member, and resilient means connected to said electroresponslve element and adjustable to vary the operating characteristic of the electroresponsive element.

JOHN W. MAY. 

